The deckhand ran to the rear deck, where the retractable helicopter landing pad was.

Horrific accident ... chief engineer Johannes Venter, with his wife Rachel, was killed aboard the Ilona IV in February 2007.

Michael Ferrugia feared a pirate attack, since the crew had been warned such attacks were possible in south-east Asian or African waters.

What he found was horrifying in a different way.

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On the helibay, he saw the legs of a person protruding from between the two hatches covering the helicopter deck, with the upper body caught underneath.

He turned to David Dixon, the second engineer, who had raised the alarm. Mr Dixon was in a panic - the man caught in the pad was the yacht's chief engineer Johannes Venter - and he could not reopen the hatch cover to free him. There was no pulse and it was clear all help was too late.

Five years on, the NSW Supreme Court is reconstructing the events of that morning to determine where and when Mr Venter died, because it could determine whether a compensation claim by Mr Venter's widow, Rachel Morrison Venter, can be heard in NSW.

Under Thai law Mrs Venter can no longer sue for damages.

If Mr Venter died in international waters, the compensation case will go to full hearing. If he died in Thai waters, Supreme Court Justice Nigel Rein will have to settle a long-standing dispute and decide if the ''law of the flag'' - the yacht is registered in Australia - takes precedent.

A logbook entry on board says the emergency alarm was raised at 10.05am - but the charts show the yacht entered Thai waters, 12 nautical miles off the small island of Ko Rok Nok, at 9.58am, meaning the Ilona IV was a few hundred metres into Thai waters.

Other evidence questions the accuracy of that assessment, and human recollection is pitched against the time recorded on CCTV footage.

The couple had started working on the yacht in April 2004 - he on a lucrative three-year $US102,000 a year contract, she as a stewardess. The South African engineer and his US-born bride married late the following year.

They were bound by a contract requiring staff to maintain a ''high standard of behaviour and appearance'' and strict confidentiality. It banned the staff from drinking alcohol when Mr Lowy or his guests were on board and allowed for random drug testing.

That February morning in 2007, the yacht had left Langkawi Island in Malaysia just before 5am, and was headed to Phuket to pick up Mr Lowy.

Breakfast was usually provided for the crew from 9 to 9.30am.

After his breakfast, Mr Venter asked Mr Dixon to help him to measure the distance between the helicopter rotor blades and the hatch covers to see if the helicopter platform could be raised by an inch.

After some preliminary work, Mr Venter lay on one hatch cover while it was still closing, preparing to reach underneath and measure the gap.

He asked Mr Dixon to bring him a measuring tool.

When Mr Dixon returned about two minutes later, he realised something was wrong before noticing the second cover had closed on top of Mr Venter.

It seemed like it took an eternity for help to arrive, but most likely was just minutes. After Mr Ferrugia came the captain and the chief officer. Mrs Venter and others arrived with a first aid bag, but were told to turn back. Mr Dixon was calmed, the hatch was opened and the body retrieved.

Then Captain Peter Oddie and chief officer Derek Barker went to the captain's office, had a cup of tea to calm their nerves and made three phone calls: one to Mr Lowy, one to a maritime lawyer in Britain and one to the ship's agent in Langkawi.

What was said has not yet been revealed.

Only then did they turn the yacht around and make the logbook entry which estimated that the alarm had been raised at 10.05am.

Both said they had believed this was the best estimate.

But Mr Ferrugia believes it was about 9.50am when Mr Dixon first called for help. Mr Dixon estimates it was 10 am.

During preliminary court proceedings last month it suddenly emerged that CCTV footage of that morning existed.

The footage showed Mr Venter had been working on the rear deck for 34 minutes before the alarm was raised. But the clock on the CCTV showed the accident occurred at 1.40am.

Mr Dixon said the CCTV clock was set to GMT, eight hours behind Malaysian time, meaning the alarm might have sounded at 9.40am, well before the ship entered Thai waters.

Others insisted Mr Venter never left breakfast before 9.30am, and the alarm could not have been raised before 10.04am and the clock must have been wrong.